One common form of display utilizes poster displays usually located at strategic road junctions for maximum effect. Such posters are commonly pasted on large display boards and remain for the time period paid for, after which the poster is replaced. A major disadvantage of the poster display is that it is restricted to displaying one poster at a time.
In order to maximize the available net display area, various systems have been developed which allow several, usually not more than three, separate advertisements to be displayed on the same display area. One system uses a rotating screen which contains two advertisements, one of which is visibly displayed at a time.
A second system utilizes a plurality of rotatable triangular slats which allows three separate advertisements to be shown. Each advertisement occupies the whole display area and is cut into strips to enable the slats to be rotated. The slats can be rotated at regular intervals so that each of the three advertisements is consequently displayed.
These existing systems are also limited in that in order to change the one or more of the advertisements, it is necessary to physically replace the poster in situ.
One of the methods for forming an image on a surface is electrophotography. Electrophotography forms a latent image on a photoconductor which is then developed using toner. The toner image is then transferred to a substrate.
Another technique for non-contact printing and imaging is ionography. An example of ionography, by the transfer of electrostatic images on to a dielectric surface using toner, is described in U.S. Pat. No. 5,289,214 to Zur.
Computer controlled display systems are usually based on some kind of projection of an image. The practical solutions, due to the limited power of the lamp are such that the image cannot be seen with a good contrast in outdoor applications, due to the high brightness of the ambient sunlight.
This invention works in reflection mode like the classical poster display, that is it uses the ambient light as light source.